package leetcode;

public class LeetCodeMain104 {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode head=new ListNode(-1);
        ListNode tail=head;
        if (l1==null&&l2==null){
            return head.next;
        }
        while (l1!=null&&l2!=null){
            if (l1.val<l2.val){
                tail.next=l1;
                l1=l1.next;
                tail= tail.next;
            }else {
                tail.next=l2;
                l2=l2.next;
                tail= tail.next;
            }
        }
        if (l1!=null){
            tail.next=l1;
        }else if (l2!=null){
            tail.next=l2;
        }
        return head.next;
    }
}
